This invention relates to the structure of an eye hole for roping reinforced by grommet metal fittings as in sheet-like articles, and is more particularly related to an eye hole for roping. The hole is reinforced in such a sequence that first an incised hole covered with a plurality of tongues created by radially incising the sheet-like material is made in a part of the sheet. A male grommet is inserted through the incised hole, and the tongues and the peripheral region of the incised hole are doubled over along the outer circumference of the inserted male grommet and both are pressed together while being enfolded by the male grommet by itself or between the male grommet and a female grommet or between the male grommet and a ring. Thus, the single male grommet, or the male grommet and the female grommet or the male grommet and the ring are securely fixed on the sheet body.
In this connection, the term "sheet-like articles" shall mean finished goods made of various kinds of "sheet-like materials", for example, canvas and other fabrics, cloths impregnated or coated with rubber or plastics, leathers, plastic film or sheet reinforced with thread or cloth, knitted or braided goods, netted fabric of close texture, thick pieces of plastic film or sheet, and others. As for the term "eye hole for roping", it shall mean a hole through or on which a rope of hemp, cotton or wire, small-gauge cord, and the like are passed or fitted, inclusive of a metal clasp hole through or on which a hook or stop fittings are passed or hung.
As a rule, a sheet body structure such as a tent, hood, covering, curtain, and such need several holes therein through which ropes, cords, etc. of hemp, cotton or wire pass which are used at the time the sheet body structure is set up. In the same way, sheet body formations such as rucksacks, bags, waist belts and the like which are formed of canvas, leather, reinforced plastic sheet and so on, are normally provided with holes through or on which ropes or buckles are passed or fitted. Such holes referred to here as eye holes for roping are usually reinforced by grommet metal fittings which line these holes.
The process widely used heretofore for reinforcing the eye hole for roping is as shown in FIG. 1, that is, first a circular through-hole (3) is formed by punching in the predetermined position of the eye hole (12A) for roping to be set in the sheet body (1), next the cylindrical portion (41) of the male grommet (4) is inserted into the through-hole (3), then the female grommet (5) is disposed onto the male grommet (4) from the reverse side of the sheet body (1), and lastly the female grommet (5) is tightly fastened and protected from falling off by the upper part (41a) of the cylindrical portion(41) of the male grommet (4), which upper part (41a) expands open and then turns down and inwards.
The grommet metal fittings not only perform the function of protecting the sheet body from fraying, further giving a sense of beauty or stability, but also impose an effective check on the enlargement of the hole and prevent the sheet body from tearing when a tensile force is applied to a rope which passes through the eye hole. In conventional articles, however, both the male grommet (4) and the female grommet (5) hold only the peripheral region of the through-hole (3) between themselves, and are simply attached to the region of the through-hole. Accordingly, when a large amount of force is applied to the rope, this force is applied only to the side of the through-hole placed under tension, and as a result, the grommet metal fittings often fall off due to tearing of the through-hole or the enlargement of the through-hole itself.
Furthermore, the above-mentioned defect is accelerated if during manufacture, the through-hole is made large in order to make the grommet-setting job easy to perform or for purposes of automation. In such a situation, various measures have been taken, for example, by strengthening the peripheral region surrounding the eye hole (2A) with the sheet body member being folded doubly or trebly, by increasing the number of eye holes with the object of dispersing the tension and by enlarging the breadth of the flange portion (42) of the male grommet or magnifying the size of the outer diameter of the female grommet in order to prevent these grommet metal fittings from falling off. These measures have had little effect in proportion to the trouble and expense needed to implement them. Additionally, the waste produced at the time of punching the holes in the sheet body often eats into the edge of the hole which tends to lead to the inferiority of punching, thereby causing various problems in the automation of punching the holes into the sheet body and setting the grommet therein.
Many structures comprised of sheet-like materials of various kinds, for example, warehouses, gymnasiums, pavilions, and the like have been constructed. The eye holes used in such constructions are required to have great tensile strength since these structures must be resistant to both their own weight and also to the large wind pressure to which they are subjected. Additionally, the eye holes must have durability equal to the sheet-like materials used (common canvas, plastic-coated canvas, or others) which have become physically stronger and more durable. It is almost impossible for an eye hole prepared according to the prior art, however, to meet the foregoing requirements.
On the other hand, it was impractical up to this time to provide eye holes for roping directly on stretchy articles comprised of for example webs of rough texture or knittings, jute-woven packing sheets, grain bags, sundry goods of victoria lawn or mosquito net cloth, and others, since the through-holes prepared on such articles readily become enlarged by tension. As a countermeasure, these holes are reinforced by taking advantage of some cloth as strong as possible in preparing for the eye holes, otherwise, referring to the bags in particular, there was no alternative but to form the through-holes for roping by folding back about the opening part of the bag. This is a troublesome and expensive job.